Btrfs: make sure roots are assigned before freeing their nodes

If we fail to load the chunk tree we'll call free_root_pointers, except we may
not have assigned the roots for the dev_root/extent_root/csum_root yet, so we
could NULL pointer deref at this point.  Just add checks to make sure these
roots are set to keep us from panicing.  Thanks,

Signed-off-by: Josef Bacik <jbacik@fusionio.com>

1 files changed, 21 insertions, 18 deletions

diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 1b03f8393a69..4bdb0528688a 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -1987,30 +1987,33 @@ static void free_root_pointers(struct btrfs_fs_info *info, int chunk_root)
 {
         free_extent_buffer(info->tree_root->node);
         free_extent_buffer(info->tree_root->commit_root);
-        free_extent_buffer(info->dev_root->node);
-        free_extent_buffer(info->dev_root->commit_root);
-        free_extent_buffer(info->extent_root->node);
-        free_extent_buffer(info->extent_root->commit_root);
-        free_extent_buffer(info->csum_root->node);
-        free_extent_buffer(info->csum_root->commit_root);
-        if (info->quota_root) {
-                free_extent_buffer(info->quota_root->node);
-                free_extent_buffer(info->quota_root->commit_root);
-        }
-
         info->tree_root->node = NULL;
         info->tree_root->commit_root = NULL;
-        info->dev_root->node = NULL;
-        info->dev_root->commit_root = NULL;
-        info->extent_root->node = NULL;
-        info->extent_root->commit_root = NULL;
-        info->csum_root->node = NULL;
-        info->csum_root->commit_root = NULL;
+
+        if (info->dev_root) {
+                free_extent_buffer(info->dev_root->node);
+                free_extent_buffer(info->dev_root->commit_root);
+                info->dev_root->node = NULL;
+                info->dev_root->commit_root = NULL;
+        }
+        if (info->extent_root) {
+                free_extent_buffer(info->extent_root->node);
+                free_extent_buffer(info->extent_root->commit_root);
+                info->extent_root->node = NULL;
+                info->extent_root->commit_root = NULL;
+        }
+        if (info->csum_root) {
+                free_extent_buffer(info->csum_root->node);
+                free_extent_buffer(info->csum_root->commit_root);
+                info->csum_root->node = NULL;
+                info->csum_root->commit_root = NULL;
+        }
         if (info->quota_root) {
+                free_extent_buffer(info->quota_root->node);
+                free_extent_buffer(info->quota_root->commit_root);
                 info->quota_root->node = NULL;
                 info->quota_root->commit_root = NULL;
         }
-
         if (chunk_root) {
                 free_extent_buffer(info->chunk_root->node);
                 free_extent_buffer(info->chunk_root->commit_root);